The present invention relates to a microsphere containing electrochemical sensor.
Electrochemical biosensors are well known. They have been used to determine the concentration of various analytes from biological samples, particularly from blood. Electrochemical biosensors are described in U.S. Pat. Nos. 5,413,690; 5,762,770 and 5,798,031; as well as in International Publication No. WO99/13101, each of which are hereby incorporated by reference.
An electrochemical biosensor typically includes a sensor strip and a sensor instrument. The sensor strip includes a space that holds the sample to be analyzed, may include reagents to be released into the sample, and includes an electrode set. The electrode set normally includes an insulating substrate, and electrodes that contact the sample, which have contact pads for electrically connecting the electrodes to the sensor instrument. The region of the electrodes where sample analysis actually takes place, the sensing region, typically receives the sample from the top, or from the side via a capillary channel defined by substrate and a cover on the substrate. Often, a reagent is present on the sensing region, to aid in electrochemical analysis. The reagent dissolves into the sample on contact.
Numerous methods have been used for controlling flow and enhancing performance of in vitro diagnostic devices. Birch and Burns (EP 0255291) described the use of a thin (ca. 200 micron) reaction zone over an electrochemical cell to measure analyte concentrations. Numerous inventions based on porous and bibulous (sample-carrying or -filtering) matrices have been described (e.g., Vogel et al. U.S. Pat. No. 4,477,575; Burkhardt et al. U.S. Pat. No. 4,810,470; Daffern et al. U.S. Pat. No. 4,994,238; Kuo et al. EP 0895084; Kuhn, Ochs and Morris U.S. Pat. No. 5,385,846; Douglas et al. U.S. Pat. No. 5,948,695). Hildenbrand et al. (U.S. Pat. No. 5,916,156) disclosed the use of a porous graphite web as a counter electrode and a sample capillary, separated from the working electrode by a non-conductive porous matrix. Hughes and Chambers (WO 9913101) disclose the use of a mesh layer to transport sample and partially occlude a sample chamber, thereby reducing the required sample volume. McAleer et al. (U.S. Pat. Nos. 5,708,247, 5,951,836) described the use of fillers containing both hydrophobic and hydrophilic surface regions to form a network, thereby reducing biosensor sensitivity to hematocrit and temperature.
An amount of sample sufficient to contact the sensing region and fill the path to the sensing region (i.e., a capillary channel) is necessary for analysis with a sensor strip. The amount of sample available for analysis is often small, and especially is the case of blood, it is desirable to minimize the amount of sample necessary. Accordingly, it would be desirable to minimize the volume of sample needed.
In one aspect, the invention is a sensor strip, including an electrode substrate, an electrode set, on the electrode substrate, and microspheres.
In another aspect, the invention is a method of making a sensor strip, including forming an electrode set on an electrode substrate; forming a channel leading to the electrode set; and inserting microspheres into the channel.
As used herein, the phrase xe2x80x9celectrode setxe2x80x9d0 is a set of at least two electrodes, for example 2 to 60, or 3 to 20, electrodes. These electrodes may be, for example, a working electrode, a counter electrode, and a reference electrode.
As used herein, the term xe2x80x9cmicrospheresxe2x80x9d0 is a plurality of particles, but does not require that the particles are spheres; rather they may have any shape. Furthermore, the term xe2x80x9cmicrospheresxe2x80x9d0 also does not limit the size of the particles; they may be any size suitable to fit a plurality onto the sensing region of a sensor strip, or into a channel leading to the sensing region of a sensor strip.
Other features and advantages of the present invention will become apparent from the following detailed description. It should be understood, however, that the detailed description and the specific examples, while indicating embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.